plot "truc.txt" using 1:2 title "2,1" index 0 with lines, "truc.txt" using 1:2 title "2,10" index 1 with lines, "truc.txt" using 1:2 title "2,100" index 2 with lines, "truc.txt" using 1:2 title "100,10" index 3 with lines, "truc.txt" using 1:2 title "100,100" index 4 with lines
